use strict;
use warnings;

my $str = <<STR;
Errors: 0 failed
Errors: 01 failed
Errors: 1 failed
Errors: 10 failed
Errors: None failed
Ben10 failed
STR

open my $fIn, '<', \$str;

while (<$fIn>) {
    print if /\b(?!0+\b)\d{1,9} failed/;
}